Following [1]}, we introduce the calculus in the \(\kappa \) -formalism by means of the \(\kappa \) -differential \(d_\kappa x\equiv dx_{\lbrace \kappa \rbrace }\) , given by the differential of the \(\kappa \) -numbers
\(d_\kappa x={dx\over \sqrt{1+\kappa ^2\,x^2}} \ ,\) 
